This invention relates to directional drilling tools. In particular, the invention relates to directional drilling tools which are used to control the direction of drilling of bore holes.
Changes in the direction of drilling of bore holes are required for a number of reasons. The most frequent reason is to change from vertical drilling to horizontal drilling or drilling at any particular angle other than vertical. Horizontal drilling has been known for many years and there are a number of established methods of changing the direction from vertical drilling to horizontal drilling. For example long radius drilling which is used for accessing oil reservoirs in remote locations, under cities, offshore or to avoid geological isolation.
Medium radius drilling is used for pinnacle relief, fractured formations and gas and water coning. Short radius drilling can be used for all these applications. The particular method used is chosen based on the economic considerations of the particular well.
The most common existing method to change the direction of drilling is to use a bent support for the drill bit or a xe2x80x9cbent subxe2x80x9d as it is often referred to. Typically a drill bit is used which is powered by a motor and the bent sub is positioned behind the motor. It is also possible for the bent sub to be positioned in front of the motor. The bent sub effectively causes the axis of rotation of the drill to be at a different angle to that of the drill pipe. Continuous drilling with the bent sub causes continuous changes of direction which results in a curved well hole in the direction of the bend of the bent sub. When the required curvature has been achieved drilling can be stopped and the bent sub changed for a straight sub to resume straight drilling.
Alternatively, the entire drill pipe can be rotated at the surface resulting in a small rotation of the bent sub, motor and drill bit assembly. The bend of the bent sub is now positioned in a different direction and drilling can be resumed in this different direction.
Directional sensors such as gyroscopic sensors are used to check the progress and direction of the drilling to establish what adjustments to the drilling angle are required.
A disadvantage of this existing method of directional drilling is that the drilling tool has to be removed from the bore hole and changed before drilling in the straight direction can be recommenced. This results in an expensive operation and increases the time to complete the required drilling.
A further disadvantage is that when drilling is restarted in a new direction it is often the case that the drill bit kicks in an unpredictable direction due to unevenness in the hardness of the formation at the point of stoppage of the drill head.
A further disadvantage with this known method is that control of the direction of the drill bit is inaccurate because it relies on rotation of the whole of the drill pipe which can result in unpredictable degrees of rotation of the drill bit. Furthermore in some applications such as with the use of continuous drill pipe or coiled tubing it is not practical to rotate the drill pipe.
GB-A-2271795 relates to a directional drilling tool in which a drill bit support is arranged upon a main support by means of a cam surface such that rotating of the drill bit support with respect to the main support cause the drill bit support to be oriented in a different direction. A disadvantage of this tool however is that the angle of the drilling tool is fixed by the shape of the cam profile which is preset and can not be changes during the drilling process, without coming back out and re-fitting an alternative tool with a different cam profile. This limits the flexibility of the drilling process.
It is an objective of this invention to provide a means of conveniently adjusting the orientation of a down hole actuation tool.
According to the present invention there is provided a variable orientation downhole actuation tool comprising a first part which is adapted to be fixed with respect to the end of a down hole tube and a second part which is adjustable with respect to the first part, characterized in that the first and second parts are adjustable with respect to each other in any two of the three possible angles; said three possible angles being the so-called Euler angles, namely the included angle or bend of a respective reference axis, the plane of included angle, or direction, and the rotation of the first body about its reference axis.
Preferably the comprises a third part such that the said third part is adjusted by at least one of the possible angles with respect to the second part which second part is adjusted by a further of the possible angles with respect to the first part.
Preferably a passageway is provided between the first and second parts for the conveyance of material, gas, liquid, solid or a combination thereof.
According to another aspect of the present invention there is provided a variable orientation downhole actuation tool comprising a first part which is adapted to be fixed with respect to the end of a down hole tube and a second part whose orientation is adjustable with respect to the characterized in that the first part and the second part includes at least one cammed surface and at least one corresponding cam follower respectively, the cammed surface being at an inclination to the second part""s axis, such that movement of the cam follower relative to the cammed surface causes a change of inclination of the second part relative to the first part.
Preferably the first part and the second part includes a first and a second cammed surface and a first and a second corresponding cam follower respectively, relative movement of the first cammed surface and first cam follower causing a change of inclination of the second part relative to the first part in a first plane, relative movement of the second cammed surface and second cam follower causing a change of inclination of the second part relative to the first part in a second plane different to the first plane.
According to a further aspect of the present invention there is provided a variable orientation downhole actuation tool comprising a first part which is adapted to be fixed with respect to the end of a down hole tube and a second part whose orientation is adjustable about a pivot means with respect to the first part characterized in that the first part includes a moveable bearing surface and the second part includes a corresponding bearing the bearing surface and bearing being moveable in two orthogonal planes such that the second part may be pivoted about the pivot means in two orthogonal planes in respect of the first part.
Preferably the first and second parts include engaging means that allow torque to be transmitted from the first part to the second part.
According to another aspect of the present invention there is provided a method of forming windows in borehole casings by means of a variable orientation downhole window forming tool comprising a first part which is fixed with respect to the end of a down hole tube and a second part which is adjustable with respect to the first part, characterized in that the forming tool is run in hole with a closely fitting straight orientation and then a bend is set to bring the window forming tool into contact with the casing upon further advancement of the window forming tool.
By embodiments of the invention efficient means of fast rotation and transmission of high torque of one of the first and second parts relative to the other are provided.
Also, strong means of coupling one of the first and second parts to the other member to another to resist reaction forces is provided.
It is a further aspect of this invention to provide means of supplying mechanical rotary power to an assembly on the actuation tool.
The actuation tool of the invention may also be used for milling windows in casing that lines a previously drilled borehole. Diameter is a severe constraint and by means of the invention it is possible to run in hole with a closely fitting straight assembly and then to set a bend to bring the cutter into contact with the casing.
Furthermore, in order to make a rapid change in direction in a short drilled distance, it is advantageous that the bend must be close to the bit, while the bit must be supported by a robust thrust bearing to permit motor shaft rotation under heavy loads. It is also advantageous that a short and simple bottom hole assembly is likely to be much more reliable and much more easily integrated with instrumentation and surface handling equipment. The present invention further provides an adjustable bend, adjustable plane of bend, thrust bearing, rotating motor shaft and passage for drilling fluid in one integrated joint close to the bit.
It will be evident that the invention may be used for pointing without necessarily rotating, such as without limitation for directing a fluid or plasma or other cutting or welding jet, arc or implement. It may also without limitation be used for orbiting a rotating abrasive or cleaning head for cleaning, cutting or dressing casing and casing joints or for expanding casing by orbiting side force.